Method for electrostatic duplication

ABSTRACT

A latent image, responsive to development by electroscopic particles, is formed on a dielectric surface by contacting that surface with an image of polar material carried on a duplicating surface; the image on the duplicating surface is obtained by transferring the polar material thereto imagewise from an intermediate master.

United States Patent 1191 Wright [4 Dec. 31, 1974 METHOD FOR ELECTROSTATIC 3,505,955 4/1970 Ritzerfeld ll7/36.l 3,579,330 5/1971 Cunningham et a1 96/1 R DUPLICATION 3,681,066 8/1972 McGuckin 96/1 R [75] In ent obe t J- rig t, an r 3,681,071 8/1972 Donald 96/l.8 Australia 3,706,553 12/1972 Menz 117/l7.5

, 7 [73] Assignee: Research Laboratories of Australia 3748I2S 7/1973 McNauy H Pty. Limited, South Australia, Australia Primary Examiner-Michael Sofocleous [22] Filed: Mar. 14 1973 Attorney, Agent, or Fmn-Kmzer, Plyer, Dorn &

McEachran [21] Appl. No.: 341,065

[30] Foreign Application Priority Data [57] ABSTRACT Apr. 10, Australia A latent image responsive to development elect scopic particles, is formed on a dielectric surface by 117/37 contacting that surface with an image of polar mate- 1 rial carried on a duplicating surface; the image on the i CL g 8 13/10, l3/16 duplicating surface is obtained by transferring the 1 Field of Search 1 37 polar material thereto imagewise from an intermediate R, l S, l D, l LY, l0, master [56] Referenees Cite 11 Claims, 4 Drawing Figures UNITED STATES PATENTS 3,479,953 11/1969 Ritzerfeld 1l7/36.1

1 METHOD FOR ELECTROSTATIC DUPLICATION This invention relates to electrostatic duplication, and in particular relates to a method in which electrostatic differences are induced in a dielectric surface by contact with an image bearing drum or roller.

Duplicating methods are known in which a master is prepared by placing a tissue with a pressure transferable coating thereon against the back surface of a paper sheet or the like and typing or writing or drawing the desired information on the front surface of the sheet, thereby producing a reverse reading copy of the information on the back of the sheet by transfer of pressure transferable coating material from the tissue to said surface. The pressure transferable material contains alcohol soluble dyes or the like which will mark the surface of an alcohol wetted image receiving member placed in contact therewith. Further alcohol wetted image receiving members are contacted in turn with the reverse reading image bearing surface to produce the required number of copies.

It is also known to reproduce information on electrographic recording members by contacting the dielectric surface of such recording members with a triboelectrically different pressure inducing means in patterned form to cause imagewise charging of said dielectric surface in patterned form on separation ofv the two members, as disclosed by Cunningham, et al., in US. Pat. No. 3,579,330.

The prior art duplicating methods previously described have certain disadvantages. For instance the spirit duplicating process involves the handling of a tissue with an easily displaced pressure transferable coating which contains large quantities of soluble dye stuffs and is inconvenient and dirty to handle and use, and in addition produces duplicated copies of poor definition due to diffusion of the alcohol dissolved dye on the surface of the image receiving member.

The Cunningham method generally requires the master to be in the form of a relief image to produce electrostatic charge patterns of maximum contrast on the surface of the dielectric recording member in order that development of the so formed latent image in a liquid dispersed toner of the type used in electrophotographic office copying machines and the like may produce images of maximum contrast and with clean backgrounds. When the Cunningham method is used with a planar master the high contact pressures used invariably produce low contrast images due to the relatively uniform deformation of the dielectric layer of the image receiving member which occurs when the master sheet and image receiving member are pressed into contact with each other.

We have now found that it is possible to induce on the dielectric surface .of an electrographic recording member latent images by pressure contact with a duplicating surface containing thereon a suitable imaging deposit wherein such latent images can be developed by attraction thereto of electroscopic marking particles and the contrast of said developed image may be enhanced by provision in the non-image areas of the duplicating surface of material substantially incapable of imaging said dielectric surface by pressure contact. Advantageously the duplicating surface may be cylindrical in form. Additionally the imaging deposit on such duplicating surface contains a polar material which can act as a electron or ion donor or receptor when contacted with the dielectric surface of the recording member.

Thus the present invention relates to a method for electrostatic duplication in which a transferable deposit in image form is produced on one surface of an intermediate master sheet, said transferable deposit being subsequently transferred at least in part to a second duplicating surface to form an imaging deposit thereon. The dielectric surface of an electrographic recording member is then contacted with said duplicating surface to form a latent image on the dielectric surface in areas corresponding to the imaging deposit which latent image is developed by contacting said latent image bearing dielectric surface with electroscopic marking particles.

In order to carry out the present invention, the information that is required to be duplicated is typed or written or otherwise impressed on the surface of a paper sheet or the like to produce an intermediate master using a marking material a transferable composition which contains said polar material. The image on such intermediate master is produced as a right way reading copy.

in one embodiment, the intermediate master is then passed through the nip of a pair of rollers so that its image bearing surface contacts the surface ofa resilient relatively insulating duplicating roller to transfer at least portion of the image deposit to the surface of said duplicating roller to form a wrong way reading imaging deposit thereon. A recording member of the electrographic type is then passed through the nip of said rollers so that its dielectric surface contacts the imaging deposit bearing surface of the duplicating roller to form a latent image of apparent negative polarity on the said dielectric surface thereof. The latent image is developed by contacting said surface with a liquid dispersion of electroscopic marking particles such as for instance a toner of the type used in electrophotographic office copying machines and the like. Further image receiving members are processed in the same manner to produce the desired number of copies.

in the embodiment previously described, the resilient relatively insulating surface of the duplicating roller may be formed from a variety of materials, such as polyurethane, polyethylene, synthetic rubbers and the like, said composition being chosen in relation to the dielectric surface of the recording member to be sub- .stantially incapable of producing any developable latent image on the dielectric surface of said recording member when contacted therewith in the absence of an imaging deposit. For example we have found that when the dielectric layer of the recordingmember consists of polyvinyl butyral resin the resilient relatively insulating layer of the duplicating roller may consist of a nitrile rubber, polyurethane or the like.

In a second embodiment of this invention the duplicating surface is not required to be resilient, although it is still necessary that the outer surface should be incapable of imaging the dielectric surface of the recording member in the absence of an imaging deposit. in this embodiment contact of the dielectric surface of the recording member with the imaging deposit on the duplicating drum may be assisted by the use of a resilient pressure roller, such as a synthetic rubber or polyurethane roller or the like.

In this embodiment the duplicating drum surface may be an insulator such as polyester or polytetrafluoroethylene layer or the like, to which the imaging deposit is transferred by electrostatic transfer, orpressure transfer, as desired.

It will be realised that the surface of said duplicating drum is essentially required to be electrically similar in the manner previously described to the dielectric surface of the recording member on which the duplicated copies are to be produced in order that no developable latent image is formed in areas free of imaging deposit, and that while relatively resilient synthetic rubber layers are readily adapted to receive the duplicating imaging deposit by pressure transfer means and to retain said duplicating imaging deposit when contacted with the dielectric surface of a recording member, the present invention is not limited to the use of such resilient materials, nor is it necessary to form said imaging deposit on the duplicating drum surface by pressure transfer means, other transfer methods such as electrostatic transfer, adhesive transfer, and the like being equally adaptable to the process of the present invention by one skilled in the art.

A latent image developable by attraction thereto of electroscopic marking particles can be formed on the dielectric surface of an electrographic recording member in accordance with this invention by using as imaging deposit on the duplicating surface a transferable material consisting for instance of binder such as wax, filler or pigment and non-drying mineral oil such as spindle oil, such spindle oil containing polar additives of the detergent dispersant and oxidation inhibiting types. Such composition can be prepared by milling or otherwise dipersing the wax pigment and oil in a suitable solvent. In those instances in which it is desired to produce an imaging deposit by pressure transfer the milled composition is coated on a tissue or other web as desired from which it can be transferred in image formation to the intermediate master. Alternatively such composition may be dispersed in a suitable insulating liquid such as those commonly used for toner dispersants in electrophotographic .office copying machines and the like and used to develop an electrostatic charge pattern on a dielectric or electrophotographic surface. In each case such image deposit may be transferred to the surface of the duplicating drum using pressure or electrostatic transfer methods or adhesive transfer methods as desired.

One of the advantages of the present invention lies in the possibility of using lower pressures than in prior art processes for latent image formation on the dielectric surface of the recording member during contact with the imaging deposit on the duplicating surface. It was found for instance that generally satisfactory latent image formation could be obtained at pressures ranging from to 50 psi and no increase in image density or contrast was obtained by increasing the pressure substantially above 50 psi. It appears that the purpose of pressure application is predominantly to ensure adequate contact between at least the imaging deposit and the dielectric surface of the electrographic recording member.

In order that the invention may be more fully understood, reference will now be made to the illustrations, in which:

FIG. 1 illustrates one method for the production of an image deposit on an intermediate master sheet,

FIG. 2 illustrates one method of transferring the image deposit from the intermediate master sheet to the duplicating drum surface,

FIG. 3 illustrates latent image formation in the actual duplicating process of this invention, and

FIG. 4 illustrates one method of developing the latent image on the dielectric surface of the recording member.

Referring to FIG. I in detail, a paper web 1 has coated on one surface a layer of pressure transferable material 2. The coated paper web is positioned with its coated surface in contact with an intermediate master sheet 4, and positioned in a typewriter, represented by typewriter key 5 and impression roller 6. A right way reading image deposit 3 is transferred by typing pressure from coating deposit 2 to the surface of intermediate master sheet 4.

In FIG. 2, intermediate master sheet 14 containing image deposit 13 is illustrated passing through the nip of a pair of rollers 17 and 18. Roller or drum I7 is the duplicating drum to the surface of which an imaging deposit 15 is transferred from intermediate master 14 under pressure. Residual image deposit 16 is normally left on the surface of intermediate master 14.

FIG. 3 illustrates the actual duplicating process in which a recording member 29 is passed through the nip between roller 28 and imaging deposit bearing duplicating drum 27 with its dielectric surface facing said duplicating drum 27. A developable latent image 26 is formed on said dielectric surface by contact with imaging deposit 25 on duplicating drum 27.

FIG. 4 illustrates a method of image development in which the latent image 36 on the dielectric surface of recording member 39 is immersed in an insulating liquid 41 containing in suspension electroscopic marking particles 42, contained in bath 40, image development being assisted by roller 43 to form an image deposit 44 by attraction of the marking particles to said latent image. Such developing processes are well known in the prior art and are only claimed herein in combination with the duplicating process herein described.

In order that the invention may be more fully understood reference will now be made to the following examples, but it will be realised that the formulations given are intended to illustrate the process as claimed, and are not intended in the limiting sense.

EXAMPLE I A pressure transferable coating formulation was prepared as follows:

Red pigment Cl No. 15850 20 grms Microcrystalline wax S grms Spindle Oil 20 grms Toluol (solvent) 40 grms the components were milled together in a ball mill for 16 hours, and coated on an 11 lb manifold paper to form a pressure transferable coating thereon upon evaporation of the solvent. Usable coatings were prepared weighing between 1 and 10 grms/sq meter, a weight of about 5 grms being preferred.

An intermediate master was prepared by typing to cause imagewise pressure transfer of a right way reading image deposit to a sheet of the same I 1 lb manifold paper, and this image was subsequently transferred in part to the surface of a duplicating drum. The material of the drum surface was a nitrile rubber, Durometer hardness 75 Shore A. A pressure of 50 psi used to transfer the image deposit to the drum surface.

A dielectric recording member in which the dielectric layer was polyvinyl butyral of 3 grms/sq. meter substance was pressed against the imaged duplicating drum surface as illustrated in FIG. 3 to produce a latent image thereon, which latent image was developed in a liquid dispersed toner of the type used in electrophotographic office copying machines and the like. Developable latent images were produced using imaging pressures as low as psi and no density increase was produced by increasing imaging pressure beyond 50 psi.

EXAMPLE 2 The duplicating drum surface of Example 1 was replaced with a polyurethane layer, Durometer hardness 50 Shore A.

EXAMPLE 3 The duplicating drum surface of Example I was replaced with a styrene-butadiene rubber, Durometer hardness 90 Shore A.

EXAMPLE 4 The image deposit on the intermediate master of Example l was transferred to a polyester resin coated duplicating drum surface by electrostatic transfer. Corona transfer was used, corona voltage being within the range 4kv l5kv, negative polarity being applied to the metal core of the duplicating drum.

EXAMPLE 5 polar imaging deposit thereon, contacting the dielectric surface of an electrographic recording member with at least said polar imaging deposit contained on said duplicating surface to form a latent image on said dielectric surface which is responsive to electroscopic development, and developing said latent image by contacting said dielectric surface with electroscopic marking particles. 2. A method of image formation as in claim 1 further characterised by forming said transferable image deposit on said intermediate master sheet by pressure transfer from a coated sheet.

3. A method of image formation as in claim 1 further characterised by transferring said transferable image deposit from said intermediate master sheet to said duplicating surface by pressure transfer.

4. A method of image formation as in claim 1 in which said duplicating surface is the outer surface of a cylinder.

5. A method of image formation as in claim 4 in which the outer layer of said duplicating cylinder is a synthetic rubber of Durometer hardness within the range 50 9O Shore A.

6. A method of image formation as in claim 1 in which said step of transferring is effected electrostatically.

7. A method of image formation as in claim 1 in which said step of contacting is under the application of pressure.

8. A method ofimage formation as in claim 6 further comprising the step of applying a corona voltage between the intermediate master and the dielectric surface.

9. A method of image formation as in claim 1 in which said intermediate master is a paper web.

10. A method of image formation as in claim 1 in t 11. A method of image formation as in claim 4 in which the outer layer of said duplicating cylinder is a polyester resin. 

1. A METHOD OF IMAGE FORMATION COMPRISING THE STEPS OF: FORMING A TRANSFERABLE IOAGE DEPOSIT OF POLAR MATERIAL ON ONE SURFACE OF AN INTERMEDIATE MASTER, TRANSFERRING AT LEAST PORTION OF SAID POLAR IMAGE DEPOSIT TO A DUPLICATING SECOND SURFACE TO FORM A POLAR IMAGING DEPOSIT THEREON, CONTACTING THE DIELECTRIC SURFACE OF AN ELECTROGRAPHIC RECORDING MEMBER WITH AT LEAST SAID POLAR IMAGING DEPOSIT CONTAINED ON SAID DUPLICATING SURFACE TO FORM A LATENT IMAGE ON SAID DIELECTRIC SURFACE WHICH IS RESPONSIVE TO ELECTROSCOPIC DEVELOPMENT, AND DEVELOPING SAID LATENT IMAGE BY CONTACTING SAID DIELECTRIC SURFACE WITH ELECTROSCOPIC MARKING PARTICLES.
 2. A method of image formation as in claim 1 further characterised by forming said transferable image deposit on said intermediate master sheet by pressure transfer from a coated sheet.
 3. A method of image formation as in claim 1 further characterised by transferring said transferable image deposit from said intermediate master sheet to said duplicating surface by pressure transfer.
 4. A method of image formation as in claim 1 in which said duplicating surface is the outer surface of a cylinder.
 5. A method of image formation as in claim 4 in which the outer layer of said duplicating cylinder is a synthetic rubber of Durometer hardness within the range 50 - 90 Shore A.
 6. A method of image formation as in claim 1 in which said step of transferring is effected electrostatically.
 7. A method of image formation as in claim 1 in which said step of contacting is under the application of pressure.
 8. A method of image formation as in claim 6 further comprising the step of applying a corona voltage between the intermediate master and the dielectric surface.
 9. A method of image formation as in claim 1 in which said intermediate master is a paper web.
 10. A method of image formation as in claim 1 in which said intermediate master contains a dielectric layer at least on one side thereof.
 11. A method of image formation as in claim 4 in which the outer layer of said duplicating cylinder is a polyester resin. 